The invention is related to measurement of subject""s sway by means of a method wherein a subject is placed to stand on a support surface for measurement of sway. The invention is related also to apparatus for measurement of subject""s sway.
Within many fields of medicine it is necessary to clear up a patient""s ability to keep one""s balance. This may be concerned with various tests, e.g. aptitude or performance tests, or when studying the state of health of an elderly person. This kind of testing may also provide suggestions about a neurological or other disease having effects on the balance of a subject.
Various test methods and equipment have been developed by means of which the motions of the centre of gravity and balancing reactions may be measured indirectly. In some methods a subject is placed on a platform the tilting direction and force of which may be measured. In some other methods the pressure or force caused by the feet of a subject on different points of a platform is measured. A subject""s ability to keep one""s balance is tested also by evaluating the sway of the subject by means of so called Romberg test, for example. The sway is often evaluated by eye, only. Also such a solution is presented in which a pen is attached to a shaft, and at the other end thereof the shaft is attached to a subject""s body whereby the pen draws a line on a paper describing the sway. However, the shaft must be quite long which causes that even small twisting motions of the body appear as large deviations in the description giving thus a distorted impression about the sway.
For the present, no such method or apparatus has been presented by means of which the sway itself could be measured. Measurements by means of the detectors attached directly to the body, for example, do not give good results because even small changes of the position of the joints, e.g. knees, change the position of the detector and cause vertical accelerations. As the accurate measurement of sway has not been possible, it has also been impossible to get information about the state of the health or performance of a subject by analyzing the sway. The object of tile invention is to provide a method and an apparatus for measurement of sway by which the foregoing problems may largely be solved.
To reach these objects the method according to the invention for measurement of sway is characterized by the features defined by claim 1. Further embodiments of the method of the invention are defined by claims 2 to 4.
The apparatus according to the invention for measurement of sway is characterized by the features defined by claim 5. Further embodiments of the apparatus of the invention are defined by claims 6 to 8.
The advantages of the method and apparatus of the invention include that the real sway motion in relation to a fixed supporting surface, e.g. floor, may be measured. Instantaneous or cumulative values of sway motion variables may be measured, and the sway motion may be registered in a memory and then be analyzed with various mathematical methods.